Message-ID: <b60d845e-5bea-4d85-a400-8a579a3e28b9@socionext.com>
Date: Mon, 3 Feb 2025 17:03:03 +0900
From: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To: Niklas Cassel <cassel@...nel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Krzysztof Wilczyński <kw@...ux.com>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Arnd Bergmann <arnd@...db.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
 Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 3/3] misc: pci_endpoint_test: Fix irq_type to convey
 the correct type

Hi Niklas,

On 2025/01/31 21:10, Niklas Cassel wrote:
> On Fri, Jan 31, 2025 at 07:16:54PM +0900, Kunihiko Hayashi wrote:
>> Hi Niklas,
>>
>> On 2025/01/29 20:58, Niklas Cassel wrote:
>>> On Tue, Jan 28, 2025 at 08:02:31PM +0530, Manivannan Sadhasivam wrote:
>>>> On Wed, Jan 22, 2025 at 11:24:46AM +0900, Kunihiko Hayashi wrote:
>>>>> There are two variables that indicate the interrupt type to be
> used
>>>>> in the next test execution, "irq_type" as global and
> test->irq_type.
>>>>>
>>>>> The global is referenced from pci_endpoint_test_get_irq() to
> preserve
>>>>> the current type for ioctl(PCITEST_GET_IRQTYPE).
>>>>>
>>>>> The type set in this function isn't reflected in the global
> "irq_type",
>>>>> so ioctl(PCITEST_GET_IRQTYPE) returns the previous type.
>>>>> As a result, the wrong type will be displayed in "pcitest" as
> follows:
>>>>>
>>>>>       # pcitest -i 0
>>>>>       SET IRQ TYPE TO LEGACY:         OKAY
>>>>>       # pcitest -I
>>>>>       GET IRQ TYPE:           MSI
>>>>>
>>>>> Fix this issue by propagating the current type to the global
> "irq_type".
>>>>>
>>>>
>>>> This is becoming a nuisance. I think we should get rid of the global
>>>> 'irq_type'
>>>> and just stick to the one that is configurable using IOCTL command.
> Even
>>>> if the
>>>> user has configured the global 'irq_type' it is bound to change with
> IOCTL
>>>> command.
>>>
>>> +1
>>
>> After fixing the issue described in this patch,
>> we can replace with a new member of 'struct pci_endpoint_test' instead.
> 
> Sorry, but I don't understand what you mean here.
> You want this patch to be applied.
> Then you want to add a new struct member to struct pci_endpoint_test?
> struct pci_endpoint_test already has a struct member named irq_type,
> so why do you want to add a new member?

Sorry for confusion.

The internal state (test->irq_type) has the state IRQ_TYPE_UNDEFINED and
the global irq_type doesn't. Then I've thought that ioctl(GET_IRQTYPE)
should not return UNDEFINED state.

However, ioctl(GET_IRQTYPE) can return with an error if the state is
UNDEFINED. This is new behavior, but not inconsistent.
So the additional irq_type is no longer necessary.

> Like Mani suggested, I think it would be nice if we could remove the
> global irq_type kernel module parameter, and change so that
> PCITEST_GET_IRQTYPE returns test->irq_type.

I see.
I'll add new patch to remove the global irq_type and replace with
test->irq_type.

> Note that your series does not apply to pci/next, and needs to be rebased.
> (It conflicts with f26d37ee9bda ("misc: pci_endpoint_test: Fix IOCTL
> return value"))

Yes, I've confirmed the conflict and I'll rebase it next.

>>
>>> But I also don't like how since we migrated to selftests:
>>> READ_TEST / WRITE_TEST / COPY_TEST unconditionally call
>>> ioctl(PCITEST_SET_IRQTYPE, MSI) before doing their thing.
>>
>> I think that it's better to prepare new patch series.
> 
> Here, I was pointing out what I think is a regression with the
> migration to selftests. (Which is unrelated to this series.)
> 
> I do suggest a way to improve things futher down (introducing a
> PCITEST_SET_IRQTYPE, AUTO), but I don't think that you need to be
> the one implementing this suggestion, since you did not introduce
> this regression.

Okay, I expect another topic after we remove the global variables.

>>
>>> Will this cause the test case to fail for platforms that only support
> MSI-X?
>>> (See e.g. dwc/pci-layerscape-ep.c where this could be the case.)
>>>
>>>
>>> Sure, before, in pcitest.sh, we would do:
>>>
>>>
>>> pcitest -i 2
>>>           pcitest -x $msix
>>>
>>>
>>> pcitest -i 1
>>>
>>> pcitest -r -s 1
>>> pcitest -r -s 1024
>>> pcitest -r -s 1025
>>> pcitest -r -s 1024000
>>> pcitest -r -s 1024001
>>>
>>>
>>> Which would probably print an error if:
>>> pcitest -i 1
>>> failed.
>>>
>>> but the READ_TEST / WRITE_TEST / COPY_TEST tests themselves
>>> would not fail.
>>>
>>>
>>> Perhaps we should rethink this, and introduce a new
>>> PCITEST_SET_IRQTYPE, AUTO
>>>
>>> I would be fine if
>>> READ_TEST / WRITE_TEST / COPY_TEST
>>> called PCITEST_SET_IRQTYPE, AUTO
>>> before doing their thing.
>>>
>>>
>>>
>>> How I suggest PCITEST_SET_IRQTYPE, AUTO
>>> would work:
>>>
>>> Since we now have capabilties merged:
>>>
> https://lore.kernel.org/linux-pci/20241203063851.695733-4-cassel@kernel.or
> g/
>>>
>>> Add epc_features->msi_capable and epc->features->msix_capable
>>> as two new bits in the PCI_ENDPOINT_TEST_CAPS register.
>>>
>>> If PCITEST_SET_IRQTYPE, AUTO:
>>> if EP CAP has msi_capable set: set IRQ type MSI
>>> else if EP CAP has msix_capable set: set IRQ type MSI-X
>>> else: set legacy/INTx
>>
>> There is something ambiguous about the behavior for me.
>>
>> The test->irq_type has a state "UNDEFINED".
>> After issueing "Clear IRQ", test->irq_type becomes "UNDEFINED"
> currently,
>> and all tests with IRQs will fail until new test->irq_type is set.
> 
> That is fine, no?
> 
> If a user calls PCITEST_CLEAR_IRQ without doing a PCITEST_SET_IRQTYPE
> afterwards, what else can the tests relying on IRQs to other than fail?
> 
> FWIW, tools/testing/selftests/pci_endpoint/pci_endpoint_test.c never does
> an ioctl(PCITEST_CLEAR_IRQ).

As mentioned above, PCITEST_GET_IRQTYPE can fail with an error, and
I understand that this will not affect the test.

Thank you,

>>
>> If SET_IRQTYPE is AUTO, how will test->irq_type be set?
> 
> I was thinking something like this:
> 
> pci_endpoint_test_set_irq()
> {
> 	u32 caps = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_CAPS);
> 
> 	...
> 
> 	if (req_irq_type == IRQ_TYPE_AUTO) {
> 		if (caps & MSI_CAPABLE)
> 			test->irq_type = IRQ_TYPE_MSI;
> 		else if (caps & MSIX_CAPABLE)
> 			test->irq_type = IRQ_TYPE_MSIX;
> 		else
> 			test->irq_type = IRQ_TYPE_INTX;
> 
> 	}
> 
> 	...
> }
> 
> 
> Kind regards,
> Niklas

---
Best Regards
Kunihiko Hayashi

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